Amorphous clay

Allophane and Imogolite. AUophane is an amorphous clay that is essentially an amorphous soHd solution of sUica, alumina, and water (82). In allophane less than one-half of the aluminum is held in tetrahedral coordinations and the Si02 to AI2O2 ratio typically varies between 1.3 and 2.0, but values as low as 0.83 have been reported. The typical morphology of allophane is cylindrical (37). AUophane may be associated with haUoysite, smectite minerals, or it may occur as a homogeneous mixture with evansite, an amorphous soHd solution of phosphoms, alumina, and water. Its composition, hydration, and properties vary. Chemical analyses of two allophane samples are given in Table 5. 

X-ray amorphous clays + H2Si04 + cations + HCOf -> cation-rich aluminosilicates + CO2 + H2O... 

In terms of soil development and the development of soil horizons, the smectites and fine-grained micas are found in younger, less weathered soils. Kaolinite and amorphous clays are found in highly weathered soils. Considering a time sequence, at the beginning of formation, soil will contain more complex clays that weather to simpler forms over time. However, it is convenient to start with a description of the simpler layer silicate clays and then describe the more complex clays. 

In addition to the crystalline clays described earlier, there are some materials that act like clays but do not have crystalline structure. Amorphous clays do not have a definite X-ray diffraction pattern and are differentiated from the crystalline clays on this basis. They are composed of mixtures of alumina, silica, and other oxides and generally have high sorptive and cation exchange capacities. Few soils contain large amounts of amorphous clays [2],... 

The partial leach protocol used a 2-h leach, using 40 ml of 0.25 M hydroxylamine hydrochloride in 0.1 M HCI at 60°C, on 1 g of the <63- j.m fraction (Cameron et al. 2004). This hydroxylamine leach is designed to dissolve secondary iron and manganese oxides. This relatively aggressive leach protocol will also dissolve phosphatic, calcareous and amorphous clay components, and will likely desorb any ions weakly bonded to other components. 

Conformations and aggregate structures of sorbed natural organic matter on muscovite and hematite. Geochim. Cosmo-chim. Ada 65 1047-1057 Nanzyo, M. Watanabe,Y. (1981) Material balance associated with phosphate sorption by amorphous clays, silica-alumina gel and synthetic goethite. Soil Sd. Plant Nutr. 27 329-337... 

Miophane and Imogolite. Allnphanc is an amorphous clay lhal is essentially an amorphous solid solution of silica, alumina, and water. Allophanc has been found most abundanlly in soils and altered volcanic ash. It usually occurs in spherical form but has also been observed in libers. 

Allophane Allophane is an amorphous clay from natural soil it is a natural aluminosilicate originating from the transformation of volcanic ashes and glasses with weathering. Allophane exists for young volcanic soil and is progressively transformed into crystalline clays, halloysite, then into kaolinite... 

Bauxite was formerly regarded as an amorphous clay mineral consisting essentially of hydrated alumina, Al Oj 2H2O. Itis a mean formula for bauxite, corresponding to x=0.5, thus AlOjjlOH). Bauxite is named after Les Baux de Provence, a locality near Arles in southern France. 

WADA K. and HARWARD M.E. 1974. Amorphous clay constituents of soils. Advances in Agronomy, 2, 211-260. 

Modification of well-ordered silicate materials such as MMT into more amorphous clay, for instance, the Cloisite clay, is crucial in order to improve the process-ability and performance of the polymer-inorganic materials. CloisitelSA possesses the largest basal spacing d spacing), that is, 31.5A as compared to the other commercial... 

Kanno [1964] described the occurrence of allophane in a humic allophane soil from the Tachikawa loam bed of a soil in Mitaka, Tokyo, derived from basaltic ash. Similarly, the amorphous clays from certain soils from basalt of northern Ireland and many other parts of the world are allophanic, and the amorphous clays in young soils derived from ultrabasic rocks such as dunite in New Zealand clearly have allophanic constituents, though these may be inseparable from gels of hydrous iron oxides, antigorites, and other secondary minerals. 

Mitchell, B. D., and V. C. Farmer, 1962. Amorphous clay minerals in some Scottish soil profiles. Clay Min. Bull 5 128-144. 

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